How probiotics could improve cognition in Alzheimer's disease patients

Taking probiotics may improve cognition in Alzheimer's disease patients, scientists have found out. After twelve weeks of treatment, they score higher on a test designed to measure the progression of cognitive impairment.

Cognitive impairment involving memory loss, orientation and language problems are important symptoms of Alzheimer's. Although it does not 'cure' them, finding ways to improve patients' cognition can significantly improve their quality of life – which is why a number of scientists have focused on this issue.

In the study published in Frontiers, a team decided to investigate the effects of probiotics on cognition. Probiotics – which come under the form of live bacteria and yeasts taken as dietary supplements – are beneficial to treat a number of conditions such as eczema, irritable bowel syndrome or tooth decay but scientists have also long suspected that they could also have a positive impact on cognition.

This is due to the microflora, gastrointestinal tract and brain communicate continuously through the nervous system, the immune system and hormones.

The first evidence of this was when probiotics showed promising results in animal studies. In mice and rats, a probiotic treatment indeed improved impaired spatial learning and memory while also reducing stress. However, this new study is one of the very few to show a positive effect in humans too.

Testing cognition

The scientists, from the Kashan University of Medical Sciences and the Islamic Azad University, in Iran, conducted a randomised, double-blind, controlled clinical trial with 60 elderly male and female participants suffering from Alzheimer's. The treatment they tested consisted in a daily dose of probiotic lactobacillus and bifidobacterium bacteria taken over a period of 12 weeks.

At the start and the end of the twelve weeks, the participants took the Mini-Mental State Examination (MMSE) test, a questionnaire that is commonly given to Alzheimer's patients to test the progression of their cognitive problems. Although the number of participants in the study was quite low, the scientists were able to see a moderate but significant improvement in the scores of those who had been given the probiotic. They progressed from 8.7 out of 30 on the test to 10.6 v 8.5 to 8.0 in the control group.

While these results suggest that the participants taking the treatment still experienced cognitive problems, they were slightly better off at the end of the trial than at the beginning. Larger studies on the longer term will now take place to investigate this in greater details.

"These findings indicate that change in the metabolic adjustments might be a mechanism by which probiotics affect Alzheimer's and possibly other neurological disorders," concluded senior author Mahmoud Salami from Kashan University. "We plan to look at these mechanisms in greater detail in our next study."